Heat Rash ?

Patient: For no reason or cause – my body temperature increases, my skin is totally red and hot to touch, and very itchy. It is almost like a heat rash, but not sure why. It almost appears like a heat stroke, but no reason. It begins in my face and head, and works its way down my body to the legs and feet. It lasts anywhere from half an hour to almost two hours. It takes place without any special activity – usually at night – when I am either laying in bed or sitting on the couch. My doctor thought it could be hot flashes, but should not be this extreme and this long. What is this or what can be causing this?